It has been well known that boric acid or boron oxide serves as a flame-proofing and fire-retardant agent for wood products. For instance, the Videen U.S. Pat. No. 3,202,570 describes procedures for introducing hydrated borate compounds in the form of fine particles throughout wood for the purpose of fire retardation. Similarly, the Quinn U.S. Pat. No. 2,030,653 describes the fire-proofing of fiberboard and similar wood products by depositing boric acid or ammonium borate therein. The Riem U.S. Pat. No. 3,629,055 describes fire-retardant hardboard obtained by treatment with a hydrolyzable ammonium borate composition to provide hardboard containing 1.3 to 7% by weight of boron made by adding the boron compound to the wet mat of fibrous slurry in the production of hardboard. These prior art patents are directed to methods of introducing boric acid or inorganic borate salts into wood products for flame-proof and fire-retardant properties.